I checked the removable red diode with a dvm in diode checker mode and with correct polarity it does light up nicelyI "ohmed out" the wires from battery compartment to switchfrom switch to diode socketeverything is normal

the problem appears to be with a switchopening the access panel revealed a small circuit board with surface mount resistorsthe problem is that it is conformal-coated so will need to start scraping that stuff off to get to resistor padsI don't mind smt soldering and resistors are aplenty but hate the scraping off partof course it's there for waterproofness...

but could it be the mechanical part of the multi position rotary knob ?

has anybody ever taken it apart ?

do tell!

_________________It is a mere question of time when men will succeed in attaching their machinery to the very wheelwork of Nature.- Nikola Tesla.

I have never taken one apart, but if it's not the diode or battery, it could be the switch or circuit board or maybe a faulty wire somewhere. Personally, I would eliminate everything mechanically, including the wires, as the culprit before messing with the circuit board.